The dependence of albedo on different factors for refreezing melt ponds in the Arctic

Abstract. Sea ice plays an important role in the heat transfer into the Arctic Ocean whereas the presence of melt ponds on sea ice complicates the scenario. In this study, we report a series of observations conducted in the central Arctic during 2012–2020 to investigate the optical and physical properties of refreezing melt ponds. From early August to early September, the albedo of ponds in the Pacific sector increases by 0.0036 d^-1, which is attributed to the changes on surface state. Based on the typical albedo, the types of melt ponds were categorized as water pond (0.14), water-ice pond (0.20), ice pond (0.25), ice-snow pond (0.39) and snow pond (0.74). Further analysis reveals the capacity of different ratios of spectral albedo on the distinction between snow ponds and unponded ice. In addition, the total albedo of ice ponds decreases with rising pond depth, and the increasing of ice lid thickness reduces the albedo while increases that of ice-snow ponds. Based on the observations, we modified a two-stream radiative transfer model, reducing its remaining error from observation by an order of magnitude. The simulation indicates ice lid thickness as the most important determining factor in the total albedo during the freezing process.